Up-drawing continuous casting method, up-drawing continuous casting apparatus, and continuous casting

ABSTRACT

An up-drawing continuous casting method according to the present invention is an up-drawing continuous casting method for forming a casting having a predetermined shape by drawing up molten metal held in a holding furnace, and includes: a step of introducing, into the molten metal, a hollow member configured to draw up the molten metal; and a step of flowing inert gas into the hollow member so as to pour the inert gas into the molten metal. The casting is formed by drawing up the molten metal with the hollow member after stopping the flowing of the inert gas into the molten metal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an up-drawing continuous casting method, an up-drawing continuous casting apparatus, and a continuous casting.

2. Description of Related Art

Japanese Patent Application Publication No. 2012-61518 (JP 2012-61518 A) describes a technique related to a free casting method (an up-drawing continuous casting method) that does not require a mold. In the free casting method described in JP 2012-61518 A, a starter is immersed into a surface of molten metal (that is, a molten metal surface), and then the starter is drawn up to lead out the molten metal. At this time, a casting having a desired sectional shape is continuously casted by leading out the molten metal via a shape determining member placed near the molten metal surface, and then cooling the molten metal thus led out.

With a normal continuous casting method, the sectional shape and the shape in a longitudinal direction are both determined by a mold. Particularly, in the continuous casting method, solidified metal (i.e., a casting) should pass through the mold, so that a casting casted hereby has a shape that extends linearly in the longitudinal direction. In contrast, in the free casting method described in JP 2012-61518 A, the shape of the casting is determined by the shape determining member movable in a direction parallel (i.e., a horizontal direction) to the molten metal surface, so that castings having various shapes in the longitudinal direction can be formed. For example, JP 2012-61518 A describes a casting formed in a zigzag shape or a helical shape in the longitudinal direction.

In the free casting method described in JP 2012-61518 A, the molten metal led out by drawing up the starter is cooled by use of coolant gas. At this time, as a flow rate of the coolant gas is increased more, a cooling rate of the molten metal is improved, thereby making it possible to raising a casting speed. However, the flow rate of the coolant gas has a limit, so there is a limit to improvement of the productivity (that is, the casting speed) by increasing the flow rate of the coolant gas in the free casting method of the related art.

SUMMARY OF THE INVENTION

The present invention provides an up-drawing continuous casting method and an up-drawing continuous casting apparatus each of which is able to improve the productivity.

An up-drawing continuous casting method according to the present invention is an up-drawing continuous casting method for forming a casting having a predetermined shape by drawing up molten metal held in a holding furnace, and includes: introducing a hollow member into the molten metal, the hollow member configured to draw up the molten metal; and flowing inert gas into the hollow member so as to pour the inert gas into the molten metal.

An up-drawing continuous casting apparatus according to the present invention is an up-drawing continuous casting apparatus for forming a casting having a predetermined shape by drawing up molten metal, and includes: a holding furnace configured to hold the molten metal; a hollow member configured to draw up the molten metal; a driving portion configured to draw up the hollow member so as to draw up the molten metal with the hollow member; and a gas supply portion configured to supply inert gas into the hollow member.

In the up-drawing continuous casting method and the up-drawing continuous casting apparatus according to the present invention, the hollow member is used as a member to draw up the molten metal. Further, the inert gas is flowed through the hollow member before the hollow member is drawn up from the molten metal, so that the hollow member is cooled off. Because of this, heat of the molten metal drawn up with the hollow member is moved to the hollow member. Accordingly, the cooling of the molten metal thus drawn up is promoted, thereby making it possible to increase a draw-up speed to draw up the hollow member and to improve the productivity of the casting.

According to the present invention, it is possible to provide an up-drawing continuous casting method and an up-drawing continuous casting apparatus each of which is able to improve the productivity.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a sectional view to describe an up-drawing continuous casting apparatus according to Embodiment 1;

FIG. 2A is a sectional view to describe an up-drawing continuous casting method according to Embodiment 1;

FIG. 2B is a sectional view to describe the up-drawing continuous casting method according to Embodiment 1;

FIG. 2C is a sectional view to describe the up-drawing continuous casting method according to Embodiment 1;

FIG. 2D is a sectional view to describe the up-drawing continuous casting method according to Embodiment 1;

FIG. 2E is a sectional view to describe the up-drawing continuous casting method according to Embodiment 1;

FIG. 2F is a sectional view to describe the up-drawing continuous casting method according to Embodiment 1;

FIG. 3 is a perspective view illustrating an example of a casting formed by use of the up-drawing continuous casting method according to Embodiment 1;

FIG. 4 is a sectional view illustrating an example of the casting formed by use of the up-drawing continuous casting method according to Embodiment 1 (blow molding);

FIG. 5 is a sectional view to describe an up-drawing continuous casting apparatus according to Embodiment 2;

FIG. 6A is a plane view illustrating an example of a shape determining member included in the up-drawing continuous casting apparatus according to Embodiment 2;

FIG. 6B is a plane view illustrating another example of the shape determining member included in the up-drawing continuous casting apparatus according to Embodiment 2;

FIG. 7 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of an up-drawing continuous casting method according to Embodiment 3, and an example of the casting thus formed;

FIG. 8 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to Embodiment 3, and an example of the casting thus formed;

FIG. 9 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to Embodiment 3, and an example of the casting thus formed;

FIG. 10 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to Embodiment 3, and an example of the casting thus formed;

FIG. 11 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to Embodiment 3, and an example of the casting thus formed;

FIG. 12 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to Embodiment 3, and an example of the casting thus formed;

FIG. 13 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to Embodiment 3, and an example of the casting thus formed;

FIG. 14 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to Embodiment 3, and an example of the casting thus formed;

FIG. 15 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to Embodiment 3, and an example of the casting thus formed;

FIG. 16 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to Embodiment 3, and an example of the casting thus formed;

FIG. 17 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to Embodiment 3, and an example of the casting thus formed;

FIG. 18 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of an up-drawing continuous casting method according to Embodiment 4, and an example of the casting thus formed; and

FIG. 19 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to Embodiment 4, and an example of the casting thus formed.

DETAILED DESCRIPTION OF EMBODIMENTS Embodiment 1

With reference to drawings, the following describes embodiments of the present invention. FIG. 1 is a sectional view to describe an up-drawing continuous casting apparatus according to Embodiment 1. The up-drawing continuous casting apparatus according to the present embodiment forms a casting having a predetermined shape while drawing up molten metal. As illustrated in FIG. 1, the up-drawing casting apparatus according to the present embodiment includes a holding furnace. 10, a hollow member 11, a driving portion 13, a cooling portion 15, and a gas supply portion 16.

The holding furnace 10 holds molten metal M1. The molten metal M1 is molten metal of aluminum or aluminum alloy, for example. The holding furnace 10 holds the molten metal M1 at a temperature of a melting point or more of a material constituting the molten metal M1. In the example in FIG. 1, molten metal is not replenished into the holding furnace 10 during casting, so that a surface level of the molten metal M1 (i.e., a molten metal surface) drops as the casting proceeds. However, molten metal may be replenished, as needed, into the holding furnace 10 during casting such that the surface level of the molten metal-is-kept constant. Note that, a-material constituting the molten metal M1 may be metal or alloy other than aluminum.

The hollow member 11 is used to draw up the molten metal M1 held in the holding furnace 10. That is, the hollow member 11 is immersed into the molten metal M1 when a casting is formed. At the time when the hollow member 11 thus immersed is drawn up, molten metal M2 (hereinafter, molten metal drawn up from the molten metal surface is referred to as the molten metal M2) is drawn up with the hollow member 11. The molten metal M2 is drawn up with the hollow member 11 due to surface film of the molten metal M2, surface tension of the molten metal M2, wettability between the molten metal M2 and the hollow member 11, and the like. After that, the molten metal M2 thus drawn up is cooled off, so that a casting M3 is formed. There is a solidification interface SIF in a boundary between the molten metal M2 and the casting M3.

The hollow member 11 includes a hollow portion 12, and inert gas supplied to the hollow member 11 flows through the hollow portion 12. The hollow member 11 is further used to pour the inert gas into the molten metal M1. A tube 17 is connected to the hollow member 11 via a joint 18. The tube 17 is connected to the gas supply portion 16. The inert gas supplied from the gas supply portion 16 is supplied into the molten metal M1 via the tube 17, the joint 18, and the hollow member 11 (the hollow portion 12). At this time, the hollow member 11 immersed in the molten metal M1 is cooled by the inert gas flowing therethrough.

A shape of the hollow member 11 can be determined according to a shape of a casting to be formed. That is, the hollow member 11 is not limited to a bar-shaped member, and may be a member having a curved portion. Further, the number of hollow members 11 may be one or more (a case where a plurality of hollow members is used will be described more specifically in Embodiment 3). In a case where a plurality of hollow members is provided, the inert gas may be poured into the molten metal M1 via at least one of the plurality of hollow members.

The hollow member 11 can be made of the same material as the material used for the molten metal M1. For example, in a case where the molten metal M1 is molten metal of aluminum or its alloy aluminum or its alloy can be used for the hollow member 11. Alternatively, the hollow member 11 may be made of a material different from the material used for the molten metal M1. In this case, in order to prevent the hollow member 11 made of a material different from the molten metal M1 from being melted into the molten metal M1, it is preferable that a melting point of the material constituting the hollow member 11 be higher than the melting point of the material used for the molten metal M1. For example, in a case where aluminum is used for the molten metal M1, the hollow member 11 can be made by use of stainless.

The driving portion 13 moves the hollow member 11 in a given direction according to a shape of the casting M3 to be formed. That is, the driving portion 13 is configured to be able to move the hollow member 11 in an up-down direction (a direction perpendicular to the molten metal surface of the molten metal M1), and in a direction (a horizontal direction) parallel to the molten metal surface of the molten metal M1. Further, the driving portion 13 may move the hollow member 11 in a diagonal direction to the molten metal surface of the molten metal M1.

When the driving portion 13 draws up the hollow member 11, the molten metal M2 is also drawn up with the hollow member 11. Then, the molten metal M2 is cooled off, so the casting M3 is formed. That is, when the driving portion 13 draws up the hollow member 11 continuously, the casting M3 is formed continuously. When a draw-up speed to draw up the hollow member 11 by the driving portion 13 is increased, a position of the solidification interface SIF can be raised. When the draw-up speed is decreased, the position of the solidification interface SIF can be lowered. At this time, the driving portion 13 may control the draw-up speed to draw up the hollow member 11 according to the shape of the casting M3 to be formed.

The cooling portion (a cooling nozzle) 15 is cooling device configured to cool off the casting M3 by spraying, on the casting M3, the coolant gas (air, nitrogen, argon, or the like) supplied from a coolant gas supply portion (not shown). When a flow rate of the coolant gas is increased, the position of the solidification interface SIF is lowered, and when the flow rate of the coolant gas is decreased, the position of the solidification interface SIF is raised. Here, since the molten metal M2 does not solidify, if the coolant gas is directly sprayed on the molten metal M2, the coolant gas undulates the molten metal M2, thereby resulting in that dimension accuracy and surface quality of the casting are decreased. In view of this, the cooling portion 15 sprays the coolant gas on the casting M3 shortly after solidifying, so as to cool the molten metal M2 indirectly. Note that the position of the cooling portion 15 can be moved to a given position in the horizontal direction or the up-down direction.

The gas supply portion 16 is connected to the hollow member 11 (the hollow portion 12) via the tube 17 and the joint 18. The gas supply portion 16 supplies inert gas at a predetermined flow rate to the hollow member 11. For example, the gas supply portion 16 is configured to be able to adjust an amount of the inert gas to supply. Since the hollow member 11 is cooled by the inert gas flowing therethrough, it is possible to control a temperature of the hollow member 11 (particularly, a temperature of the hollow member 11 at the time when the hollow member 11 is immersed into the molten metal M1) by adjusting the flow rate of the inert gas. At this time, the gas supply portion 16 may control the flow rate of the inert gas to flow through the hollow member 11, according to the shape of the casting to be formed. For example, nitrogen (N₂), argon (Ar), or the like can be used as the inert gas.

An operation of the driving portion 13, the flow rate of the coolant gas discharged from the cooling portion 15, and the flow rate of the inert gas supplied from the gas supply portion 16 are controlled by use of a control device (not shown). That is, the up-drawing continuous casting apparatus can form a casting having a given shape by controlling these parameters.

Next will be described an up-drawing continuous casting method according to the present embodiment with reference to FIGS. 2A to 2F. As illustrated in FIG. 2A, the tube 17 is first fixed to the hollow member 11 by use of the joint 18. Further, the hollow member 11 is fixed to the driving portion 13. Subsequently, as illustrated in FIG. 2B, the hollow member 11 is introduced (immersed) into the molten metal M1 by moving down the hollow member 11 while inert gas 21 is being discharged from the hollow member 11. When the hollow member 11 reaches a target position in the molten metal M1 (that is, the hollow member 11 reaches a predetermined depth), the hollow member 11 stops moving down. After the hollow member 11 stops moving down, the inert gas 21 is discharged from the hollow member 11 for a predetermined time, as illustrated in FIG. 2C. The inert gas 21 is thus poured into the molten metal M1 via the hollow member 11, so that the molten metal M1 can be cleaned. That is, impurities (hydrogen or the like) included in the molten metal M1 and causing defects (blowhole) of a casting can be removed.

After that, as illustrated in FIG. 2D, the discharge of the inert gas from the hollow member 11 is stopped. Then, as illustrated in FIG. 2E, the hollow member 11 is drawn up by use of the driving portion 13. At this time, spraying of the coolant gas from the cooling portion 15 is also started. When the hollow member 11 is drawn up, the molten metal M2 is also drawn up with the hollow member 11. Then, the molten metal M2 thus drawn up is cooled by the coolant gas sprayed from the cooling portion 15, and thus, the casting M3 is formed. By drawing up the hollow member 11 continuously by use of the driving portion 13 as such, the casting M3 is formed continuously.

At this time, the molten metal M2 is indirectly cooled off via the casting M3. That is, the coolant gas from the cooling portion 15 is sprayed on the casting M3 shortly after solidifying, so as to cool off the casting M3, so that heat of the molten metal M2 is moved to the casting M3 thus cooled off. Hereby, the molten metal M2 is cooled off. Further, in the up-drawing continuous casting method according to the present embodiment, the inert gas 21 is flowed through the hollow member 11 before the hollow member 11 is drawn up from the molten metal M1 (see FIG. 2C), so that the hollow member 11 immersed in the molten metal M1 is cooled off. Because of this, the heat of the molten metal M2 drawn up with the hollow member 11 is moved to the casting M3 and also to the hollow member 11. Accordingly, the cooling of the molten metal M2 is promoted, thereby making it possible to increase the draw-up speed to draw up the hollow member 11 and to improve the productivity of the casting.

That is, when the cooling of the molten metal M2 is promoted, the position of the solidification interface SIF, which is a boundary between the molten metal M2 and the casting M3, is lowered. Since the position of the solidification interface SIF is lowered, the driving portion 13 can increase the draw-up speed to draw up the hollow member 11 in accordance with the amount of dropping of the position of the solidification interface SIF, thereby making it possible to increase the casting speed.

After that, the hollow member 11 is kept drawn up, and when a tip end 19 of the hollow member 11 reaches near the molten metal surface (may be on the molten metal surface) of the molten metal M1 as illustrated in FIG. 2F, the inert gas is poured into the hollow member 11. When the inert gas is poured into the hollow member 11 as such, it is possible to restrain the tip end 19 of the hollow member 11 from being closed.

FIG. 3 illustrates an example of the casting formed by use of the up-drawing continuous casting method described above. A casting 30 illustrated in FIG. 3 is configured such that a casting 31 (corresponding to the casting M3) solidifies around the hollow member 11 (indicated by a broken line). The hollow portion 12 of the hollow member 11 does not disappear but remains. Note that the casting 30 in FIG. 3 shows a shape obtained by cutting off an upper part (a portion where the casting M3 does not solidify) of the hollow member 11 after the casting is formed.

Note that the up-drawing continuous casting method described above is an example, and the up-drawing continuous casting method according to the present embodiment is not limited to the example described above. For example, before the hollow member 11 is immersed into the molten metal M1 (see FIG. 2A), the inert gas 21 may be flowed through the hollow member 11 to cool off the hollow member 11 to a predetermined temperature in advance.

Further, in FIG. 2B, the hollow member 11 is immersed into the molten metal M1 while the inert gas 21 is being discharged from the hollow member 11. However, the discharge of the inert gas 21 from the hollow member 11 may be stopped when the hollow member 11 is immersed into the molten metal M1. Further, in a case where the hollow member 11 is immersed into the molten metal M1 while the inert gas 21 is being discharged, the discharge of the inert gas (see FIG. 2C) after the hollow member 11 has stopped moving down may be omitted. Further, a step of pouring the inert gas into the hollow member 11 near the molten metal surface of the molten metal M1, as illustrated in FIG. 2F, may be omitted.

Further, the up-drawing continuous casting method described above deals with a case where the hollow portion 12 remains after the casting is formed. However, in the up-drawing continuous casting method according to the present embodiment, the hollow portion 12 may disappear after the casting is formed. For example, in the step illustrated in FIG. 2C, when the hollow member 11 is held in the molten metal M1 for a while after the discharge of the inert gas from the hollow member 11 is stopped, part of the hollow member 11 begins to melt. When the hollow member 11 is drawn up after that, it is possible to form a casting without the hollow portion 12.

In the up-drawing continuous casting method according to the present embodiment, even in a case where the same hollow member 11 is used, the casting speed and the shape of the casting vary depending on time for holding the hollow member 11 in the molten metal M1, the heat capacity of the molten metal M1, the flow rate (coolability) of the inert gas to flow through the hollow member 11, or the like. For example, as the time for holding the hollow member 11 in the molten metal M1 is shorter, or as the heat capacity of the molten metal M1 is smaller, or as the flow rate of the inert gas to flow through the hollow member 11 is higher, the temperature of the hollow member 11 decreases and the casting speed improves.

Further, in the up-drawing continuous casting method according to the present embodiment, when the hollow member 11 reaches near the molten metal surface (may be on the molten metal surface) of the molten metal M1 (see FIG. 2F), the inert gas may be poured into the hollow member 11 to perform blow molding. FIG. 4 is a sectional view illustrating an example of a casting obtained by blow molding. A casting 30′ illustrated in FIG. 4 is configured such that a casting 32 (corresponding to the casting M3) solidifies around the hollow member 11. Further, since blow molding is performed when the casting 30′ is formed, a ball-shaped space 33 is formed in the tip end of the hollow member 11. That is, a ball-shaped structure formed in the tip end of the hollow member 11 is formed by blowing up the casting-M3 by use of the inert gas.

In the free casting method described in JP 2012-61518 A, the molten metal led out by drawing up the starter is cooled by use of coolant gas. At this time, as a flow rate of the coolant gas is increased more, a cooling rate of the molten metal is improved, thereby making it possible to raising a casting speed. However, the flow rate of the coolant gas has a limit, so there is a limit to improvement of the productivity (that is, the casting speed) by increasing the flow rate of the coolant gas in the free casting method of the related art.

In view of this, in the present embodiment, the hollow member 11 is used as a member to draw up the molten metal M1. Further, the inert gas is flowed through the hollow member 11 before the hollow member 11 is drawn up from the molten metal M1, so that the hollow member 11 is cooled off. Because of this, the heat of the molten metal M2 drawn up with the hollow member 11 is moved to the casting M3 and to the hollow member 11. Accordingly, the cooling of the molten metal M2 is promoted, thereby making it possible to increase the draw-up speed to draw up the hollow member 11 and to improve the productivity of the casting.

Moreover, in the present embodiment, the inert gas is poured into the molten metal M1 via the hollow member 11 before the hollow member 11 is drawn up from the molten metal M1. Hereby, impurities (hydrogen or the like) included in the molten metal M1, the impurities causing defects (blowhole) of a casting, can be removed, and thus, the molten metal M1 can be cleaned. This makes it possible to improve the quality of the casting to be formed.

Embodiment 2

Next will be described Embodiment 2 of the present invention. FIG. 5 is a sectional view to describe an up-drawing continuous casting apparatus according to Embodiment 2. The up-drawing continuous casting apparatus illustrated in FIG. 5 is different from the up-drawing continuous casting apparatus (see FIG. 1) described in Embodiment 1 in that a shape determining member 25 is provided. Except for the above point, the up-drawing continuous casting apparatus of Embodiment 2 is the same as the up-drawing continuous casting apparatus described in Embodiment 1, so the same reference sign is assigned to the same constituent and duplicate description is omitted.

The shape determining member 25 is a member configured to determine a shape (a sectional shape) of a casting M3 by applying, to molten metal M1, an external force (that is, a force that acts on the molten metal M1 at the time when the molten metal M1 passes through a molten metal passage portion 26), when the molten metal M1 is drawn up with a hollow member 11 to form the casting M3. The shape determining member 25 is made of ceramics or stainless, for example, and is placed near a molten metal surface. In an example illustrated in FIG. 5, the shape determining member 25 is placed so that a principal plane (a bottom face) on a lower side of the shape determining member 25 makes, contact with the molten metal surface. Since the bottom face of the shape determining member 25 makes contact with the molten metal surface, it is possible to prevent an oxide film formed on a surface of the molten metal M1 and foreign matters floating on the surface of the molten metal M1 from mixing into the casting M3. Note that, in the present embodiment, the shape determining member 25 may be placed so that the bottom face of the shape determining member 25 is opposed to the molten metal surface (that is, the bottom face of the shape determining member 25 is spaced from the molten metal surface).

FIG. 6A is a plane view illustrating an example of the shape determining member 25. Here, the sectional view of the shape determining member 25 in FIG. 5 corresponds to a sectional view taken along a line V-V in FIG. 6A. As illustrated in FIG. 6A, the shape determining member 25 has a rectangular planar shape, for example, and has, in its central part, a rectangular opening (the molten metal passage portion 26) having a length w×t and configured such that the molten metal passes therethrough.

As illustrated in FIG. 5, the molten metal M1 is drawn up with the hollow member 11, and passes through the molten metal passage portion 26 of the shape determining member 25. That is, when the molten metal M1 passes through the molten metal passage portion 26 of the shape determining member 25, an external force is applied to the molten metal M1 from the shape determining member 25, so that a sectional shape of the casting-M3 is determined.

Note that the shape determining member 25 illustrated in FIG. 6A is one example, and in the present embodiment, a shape determining member having other shapes may be used as the shape determining member. For example, the shape of the opening (the molten metal passage portion 26) of the shape determining member is not limited to the rectangular shape, and may be other shapes such as a round shape, an oval shape, and a polygonal shape. That is, the shape of the opening (the molten metal passage portion 26) of the shape determining member can be determined to a given shape according to a sectional shape (a horizontal section) of a casting to be formed.

FIG. 6B is a plane view illustrating another example of the shape determining member. The shape determining member 25 illustrated. FIG. 6A is constituted by a single plate, so the length w, t of each side of the molten metal passage portion 26 is fixed. On the other hand, since a shape determining member 25′ illustrated in FIG. 6B includes four rectangular shape determining plates 27_1 to 27_4, a length w, t of each side of a molten metal passage portion 28 can be changed.

As illustrated in FIG. 6B, the shape determining plates 27_1, 27_2 are placed so as to be opposed to each other in a lateral direction on a plane of paper (a lateral direction in the sectional view of FIG. 5). Since the shape determining plates 27_1, 27_2 are configured to be movable independently from each other in the lateral direction on the plane of paper, the length w of the molten metal passage portion 28 can be changed to a given length. Similarly, the shape determining plates. 27_3, 27_4 are placed so as to be opposed to each other in a up and down direction on the plane of paper (a depth direction in the sectional view of FIG. 5). Since the shape determining plates 27_3, 27_4 are configured to be movable independently from each other in the up and down direction on the plane of paper, the length t of the molten metal passage portion 28 can be changed to a given length. The shape determining plates 27_3, 27_4 are placed so as to make contact with upper sides of the shape determining plates 27_1, 27_2.

Since the length w, t of each side of the molten metal passage portion 28 can be changed in the shape determining member 25′ illustrated in FIG. 6B as such, the sectional shape of the casting to be formed, can be determined freely. On the occasion that the driving portion 13 draws up the hollow member 11 continuously, for example, when the shape determining plates 27_1 to 27_4 of the shape determining member 25′ are moved to change the length w, t of each side of the molten, metal passage portion 28, the sectional shape of the casting M3 can be changed continuously.

As described above, in the up-drawing continuous casting method according to the present embodiment, since an external force is applied to the molten metal M1 by use of the shape determining member, the sectional shape of the casting M3 can be determined to a given shape. That is, in Embodiment 1, the shape (the sectional shape) of the casting to be formed is determined by the shape of the hollow member 11 and the flow rate of the inert gas to flow through the hollow member 11 (that is, a cooling degree of the hollow member 11). In contrast, in the up-drawing continuous casting method according to the present embodiment, the sectional shape of the casting can be determined by use of the shape determining member in addition to the shape of the hollow member 11 and the flow rate of the inert gas to flow through the hollow member 11. Accordingly, it is possible to form the casting with accuracy.

Further, in the present embodiment, the hollow member 11 is also used to draw up the molten metal M1, similarly to Embodiment 1, so it is possible to improve the productivity of the casting. Moreover, the inert gas is poured into the molten metal M1 via the hollow member 11 before the hollow member 11 is drawn up from the molten metal M1. This makes it possible to clean the molten metal M1 and to improve the quality of the casting to be formed.

Embodiment 3

Next will be described Embodiment 3 of the present invention. Embodiments 1, 2 deal with a case where a casting is formed by use of one hollow member. Embodiment 3 deals with a case where a casting is formed by use of a plurality of hollow members. Note that the following exemplary castings are merely examples, and castings having other various shapes can be formed in an up-drawing continuous casting method according to the present invention. Note that an up-drawing continuous casting apparatus for use in the present embodiment is the same as the up-drawing continuous casting apparatus as described in Embodiments 1, 2, so duplicate-description is omitted.

FIGS. 7 to 17 are perspective views each illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to the present embodiment, and an example of the casting thus formed. For example, a plurality of hollow members may be placed so as to separate from each other (see FIGS. 7, 8, 13, 16, 17), or may be placed so as to make contact with each other (FIGS. 9 to 12, FIG. 14). Further, the plurality of hollow members may be placed linearly (FIGS. 7 to 12, FIG. 16), or may be placed in an annular shape (FIGS. 13, 14, 17). As the plurality of hollow members, hollow members different in thickness from each other may be used (see FIG. 16). As the plurality of hollow members, hollow members different in length from each other may be used (see FIG. 17). The following more specifically describes the case where a casting is formed by use of a plurality of hollow members.

FIG. 7 is a view to describe a case where a casting is formed by use of a plurality of (two) hollow members. As illustrated in FIG. 7, two hollow members 41_1, 41_2 include hollow portions 42_1, 42_2, respectively. The two hollow members 41_1, 41_2 are placed so as to separate from each other.

At the time of forming a casting, the tube 17 to supply inert gas is first fixed to the hollow members 41_1, 41_2, and further, the hollow members 41_1, 41_2 are fixed to the driving portion 13 (see FIG. 2A). After that, the hollow members 41_1, 41_2 are immersed into the molten metal M1 by moving down the hollow members 411, 41_2 while the inert gas is being discharged from the hollow members 41_1, 41_2 (see FIG. 2B). After that, when the hollow members 41_1, 41_2 reach a target position in the molten metal M1, the hollow members 41_1, 41_2 stop moving down, and the inert gas 21 is discharged from the hollow members 41_1, 41_2 for a predetermined time (see FIG. 2C).

After that, the discharge of the inert gas from the hollow members 41_1, 41_2 is stopped (see FIG. 2D), and the hollow members 41_1, 41_2 are drawn up (see FIG. 2E). At this time, spraying of the coolant gas from the cooling portion 15 is also started. When the hollow members 41_1, 412 are drawn up, the molten metal M2 is also drawn up with the hollow members 41_1, 41_2. Then, the molten metal M2 thus drawn up is cooled by the coolant gas sprayed from the cooling portion 15, and thus, a casting is formed.

In the case illustrated in FIG. 7, the two hollow members 41_1, 41_2 are placed so as to separate from each other. Accordingly, when the two hollow members 41_1, 41_2 are drawn up, the molten metal M2 is retained around the hollow members 41_1, 41_2 and between the hollow member 41_1 and the hollow member 41_2 due to a surface tension of the molten metal M2; Therefore, the casting thus formed has a shape in which the two hollow member 41_1, 41_2 are surrounded by the casting 43 to be integrated with each other.

In the case illustrated in FIG. 7, since the two hollow members 41_1, 41_2 are placed so as to separate from each other only by a predetermined distance, side surfaces of the casting 43 between the hollow member 41_1 and the hollow member 41_2 are recessed (that is, the casting 43 includes recessed portions 44). In the meantime, in a case where the two hollow members 41_1, 41_2 are placed close to each other as illustrated in FIG. 8, side surfaces of a casting 45 between the hollow member 41_1 and the hollow member 41_2 have a flat shape (or a shape close to the flat shape).

In a case where the two hollow members 41_1, 41_2 are placed so as to separate from each other as such, the molten metal M2 can be retained in a space between the hollow member 41_1 and the hollow member 412, so that it is possible to form a casting having a large volume while reducing the number of hollow members.

FIG. 9 is a view to describe a case where a casting is formed by use of a plurality of (five) hollow members. As illustrated in FIG. 9, five hollow members 51 each include a hollow portion 52. The five hollow members 51 are linearly placed so as to make contact with each other. Note that how to form a casting is the same as the method as described above, so duplicate description is omitted.

In the case illustrated in FIG. 9, when the five hollow members 51 are drawn up, the molten metal M2 is retained around the hollow members 51 due to a surface tension of the molten metal M2. Therefore, a casting formed hereby has a shape in which the five hollow members 51 are surrounded by a casting 53 to be integrated with each other.

In the case illustrated in FIG. 9, it takes sufficient time to draw up the five hollow members 51, so side surfaces of the casting 53 have a flat shape (or a shape close to the flat shape). In the meantime, in a case where when a draw-up speed to draw up the five hollow members 51 is fast, the molten metal solidifies without sufficiently retaining the molten metal M2 around the hollow members 51, so a casting formed hereby has a shape as illustrated in FIG. 10. That is, the casting has a shape in which side surfaces of a casting 54 are irregular, in other words, the casting has a shape following an outer circumference of the hollow members 51.

Further, when the draw-up speed to draw up the hollow members 51 is slowed down in the middle of the draw-up, it is possible to form a casting in which the hollow portions 52 in lower half of a casting 55 are closed as illustrated FIG. 11. That is, when the draw-up speed to draw up the hollow members 51 are slowed down in the middle of the draw-up, the lower half of the hollow members 51 begins to melt in the molten metal M1, so the hollow portions 52 in the lower half of the casting 55 can be closed. Thus, in the present embodiment, by controlling the draw-up speed to draw up the hollow members 51 according to the shape of a casting to be formed at the time when the hollow members 51 are drawn up, it is possible to form a casting having a given shape. Note that the draw-up speed at the time of forming a casting can be determined in consideration of the wettability between molten metal to use and a hollow member, and the like.

Further, in the present embodiment, the inert gas may be flowed through at least one of the plurality of hollow members. That is, it is not necessary to flow the inert gas through all the hollow members. For example, as illustrated in FIG. 12, in a case where the inert gas is flowed through four hollow members 51_1, 51_2, 51_4, 51_5 among five hollow members 51_1 to 51_5, a temperature of the hollow member 51_3 through which no inert gas flows increases in the molten metal, so that the hollow member 51_3 begins to melt in the molten metal. As a result, as illustrated in FIG. 12, a casting 56 formed hereby has a shape in which no hollow portion 52_3 is formed. Since the inert gas is flowed through the four hollow members 51_1, 51_2, 51_4, 51_5, hollow portions 52_1, 52_2, 52_4, 525 are not closed.

FIG. 13 is a view to describe a case where a casting is formed by placing a plurality of hollow members in an annular shape. As illustrated in FIG. 13, a plurality of hollow members 61 is placed in an annular shape. Further, the hollow member 61 is also placed in a central part. The plurality of hollow members 61 each includes a hollow portion 62. Note that how to form a casting is the same as the method described above, so duplicate description is omitted.

In the case illustrated in FIG. 13, when the plurality of hollow members 61 is drawn up, the molten metal M2 is retained around the hollow members 61 due to a surface tension of the molten metal M2. Therefore, a casting formed hereby has a shape in which the hollow members 61 placed in an annular shape are surrounded by a casting 63 to be integrated with each other. At this time, the hollow portions 62 are not closed, so the casting 63 has a honeycomb shape. Note that, in the case illustrated in FIG. 13, the hollow members are placed so as to separate from each other, but the hollow members may be placed so as to make contact with each other.

FIG. 14 is a view to describe a case where a plurality of hollow members 61 is placed in an annular shape without placing any hollow member in a central part. In the case illustrated in FIG. 14, when the plurality of hollow members 61 is drawn up, the molten metal M2 is retained around the hollow members 61. Therefore, a casting formed hereby has a shape in which the hollow members 61 placed in an annular shape are surrounded by a casting 64 to be integrated with each other. Further, in this case, no hollow member is placed in a central part of the annular shape, so that no molten metal M2 is retained in the central part of the annular shape. Accordingly, a cavity 65 is formed in a central part of the casting 64.

In the case illustrated in FIG. 14, it takes sufficient time to draw up the plurality of hollow members 61, so side surfaces of the casting 64 have a flat shape (or a shape close to the flat shape). In the meantime, in a case where when a draw-up speed to draw up the plurality of hollow members 61 is fast, the molten metal solidifies without sufficiently retaining the molten metal M2 around the hollow members 61, so a casting formed hereby has a shape as illustrated in FIG. 15. That is, the casting has a shape in which an outer peripheral surface and an inner peripheral surface (a surface on a cavity 67 side) of a casting 66 are irregular, in other words, the casting 66 has a shape following an outer circumference of the hollow members 61. Note that, in the cases illustrated in FIGS. 14, 15, the hollow members are placed so as to make contact with each other, but the hollow members may be placed so as to separate from each other.

FIG. 16 is a view to describe a case where a plurality of hollow members is different in thickness from each other. As illustrated in FIG. 16, hollow members 71_1, 71_2 are different in thickness from each other. That is, the thickness of the hollow member 71_1 is larger than the thickness of the hollow member 71_2. The plurality of hollow members 71_1, 71_2 include hollow portions 72_1, 72_2, respectively. Note that how to form a casting is the same as the method described above, so duplicate description is omitted.

In the case illustrated in FIG. 16, the hollow members 71_1, 71_2 are different in thickness from each other. Accordingly, when the hollow members 71_1, 71_2 are drawn up, a sectional shape (a shape of a horizontal section) of the molten metal M2 retained by the hollow members 71_1, 71_2 becomes a shape following a sectional shape of the hollow members 71_1, 71_2. That is, the sectional shape follows a shape defined by outer circumferences of two hollow members and tangents that connect the outer circumferences (two circles). Therefore, a casting formed hereby has a shape in which the hollow members 71_1, 71_2, which are different in thickness from each other, are surrounded by a casting 73 to be integrated with each other.

FIG. 17 is a view to describe a case where a plurality of hollow members is different in length from each other. As illustrated in FIG. 17, hollow members 81_1 placed in an annular shape and a hollow member 81_2 placed in a center of the annular shape are different in length from each other. That is, the length of the hollow member 81_2 is longer than the length of the hollow members 81_1. The plurality of hollow members 81_1, 81_2 include hollow portions 82_1, 82_2, respectively. Note that how to form a casting is the same as the method described above, so duplicate description is omitted.

In the case illustrated in FIG. 17, the hollow members 81_1, 81_2 are different in length from each other. Accordingly, when the hollow members 81_1, 81_2 are drawn up, a sectional shape (a shape of a horizontal section) of the molten metal M2 retained by the hollow members 81_1, 81_2 varies in a longitudinal direction of the hollow members 81_1, 81_2. That is, the hollow members 81_1 are placed in an annular shape in a region 83, and the hollow member 81_2 is placed in a center of the annular shape. Accordingly, a sectional shape of the molten metal M2 retained by the hollow members 81_1, 81_2 in the region 83 is a generally uniform round shape in the longitudinal direction of the hollow members 81_1, 81_2. Because of this, that part of a casting 85 which corresponds to the region 83 has a circular column shape 86.

Meanwhile, in a region 84, one hollow member 81_2 projects from a tip end, on a lower side, of the hollow members 81_1 placed in an annular shape. Accordingly, the sectional shape of the molten metal M2 retained by the hollow members 81_1, 81_2 in the region 84 is a circular shape that is reduced in diameter from an upper side toward a lower side in the region 84. Because of this, that part of the casting 85 which corresponds to the region 84 has a generally circular cone shape 87 (that is, a tapered shape).

Note that each of the placements of the hollow members described above is just an example, and the placement of the hollow members can be determined according to a shape of a casting to be formed in the up-drawing continuous casting method according to the present invention. Further, the exemplary placements described above can be combined appropriately. For example, a plurality of hollow members may be different in thickness and further different in length from each other.

Embodiment 4

Next will be described Embodiment 4 of the present invention. Embodiment 4 deals with a case where a mold release agent is provided in at least part of a hollow member. Note that an up-drawing continuous casting apparatus for use in the present embodiment is the same as the up-drawing continuous casting apparatus as described in Embodiments 1, 2, so duplicate description is omitted.

FIG. 18 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of an up-drawing continuous casting method according to the present embodiment, and an example of the casting thus formed. As illustrated in FIG. 18, two hollow members 101_1, 101_2 are placed so as to separate from each other. Further, the two hollow members 101_1, 101_2 include hollow portions 102_1, 102_2, respectively. A mold release agent 103_1 is provided on one of side surfaces of the hollow member 101_1 which is on an opposite side to a side facing the hollow member 101_2. Similarly, a mold release agent 103_2 is provided on one of side surfaces of the hollow member 101_2 which is on an opposite side to a side facing the hollow member 101_1. Boron nitride (BN) can be used, for example, for the mold release agent. A film thickness of the mold release agent can be around 2 μm to 10 μm, for example. Note that the material used for the mold release agent and the film thickness thereof are one examples, and they are not limited to the above.

At the time of forming a casting, the tube 17 to supply inert gas is first fixed to the hollow member 101_1, 101_2, and further, the hollow members 101_1, 101_2 are fixed to the driving portion 13 (see FIG. 2A). After that, the hollow members 101_1, 101_2 are immersed into the molten metal M1 by moving down the hollow members 101_1, 101_2 while the inert gas is being discharged from the hollow members 101_1, 101_2 (see FIG. 2B). After that, when the hollow members 101_1, 101_2 reach a target position in the molten metal M1, the hollow members 101_1, 101_2 stop moving down, and the inert gas is discharged from the hollow members 101_1, 101_2 for a predetermined time (see FIG. 2C).

After that, the discharge of the inert gas from the hollow members 101_1, 101_2 is stopped (see FIG. 2D), and the hollow members 1011, 101_2 are drawn up (see FIG. 2E). At this time, spraying of the coolant gas from the cooling portion 15 is also started. When the hollow members 101_1, 101_2 are drawn up, the molten metal M2 is also drawn up with the hollow members 101_1, 101_2. Then, the molten metal M2 thus drawn up is cooled by the coolant gas-sprayed from the cooling, portion 15, and thus, a casting is formed.

In the case illustrated in FIG. 18, the hollow member 101_1, 101_2 are each provided with the mold release agent. Because of this, no casting is formed on those side surfaces of the hollow members 101_1, 101_2 on which the mold release agents 103_1, 103_2 are provided (or even if a casting is formed, it can be removed therefrom). Accordingly, a casting 104 formed hereby has a shape following outer shapes of the hollow members 101_1, 101_2.

By providing the mold release agent in part of the hollow member as such, the shape of the casting to be formed can be determined. Further, by providing the mold release agent in part of the hollow member, melting of the hollow member can be restrained. Further, in a case where the material of the hollow member is different from the material of the molten metal, electrolytic corrosion of the hollow member can be restrained by providing the mold release agent in the hollow member.

FIG. 19 is a perspective view illustrating an example of the placement of hollow members at the time of forming a casting by use of the up-drawing continuous casting method according to the present embodiment, and an example of the casting thus formed. As illustrated in FIG. 19, two hollow members 111_1; 111_2 are placed so as to separate from each other. Further, the two hollow members 111_1, 111_2 include hollow portions 112_1, 112_2, respectively. A mold release agent 113 a and a mold release agent 113 b are provided around an upper side of the hollow member 111_1 and around a lower side thereof, respectively. A mold release agent 113 c and a mold release agent 113 d are provided around an upper side of the hollow member 111_2 and around a lower side thereof, respectively. Parts indicated by reference signs 114_1, 114_2 are parts not provided with a mold release agent (parts where the hollow members are exposed).

When a casting is formed by use of the hollow members 111_1, 111_2 illustrated on the upper-left side of FIG. 19, a casting 115 having a shape illustrated on the upper-right side of FIG. 19 is formed. In this case, in those parts 114_1, 114_2 of the hollow members 111_1, 111_2 which are not provided with the mold release agents 113 a to 113 d, the casting 115 is integrated with the hollow members 111_1, 111_2. Meanwhile, in those parts of the hollow members 111_1, 111_2 which are provided with the mold release agents 113 a to 113 d, the casting 115 is not integrated with the hollow members 111_1, 111_2, so the casting 115 is separable from the hollow members 111_1, 111_2.

Accordingly, as illustrated on the lower side of FIG. 19, an upper part 118 a and a lower part 118 b of the hollow member 111_1 can be separated from the casting 115. Similarly, an upper part 118 c and a lower part 118 d of the hollow member 111_2 can be separated from the casting 115. That is, in the example illustrated in FIG. 19, those parts of the hollow members which are provided with the mold release agents can be separated from the casting after the casting is formed.

By providing the mold release agents in the hollow member as such, castings having various shapes can be formed. Particularly, by combining the present embodiment with Embodiment 3 (the embodiment in which a plurality of hollow members is placed), it is possible to form castings having various shapes.

A casting formed by use of the up-drawing continuous casting method described in Embodiments 1 to 4 includes a matrix having a unidirectional solidified structure extended in a longitudinal direction and a hollow member extended in the longitudinal direction as a dualphase. On that account, the casting has excellent longitudinal strength. At this time, a plurality of hollow members may be included therein as the hollow member. Further, the hollow member may be made of the same material as a material constituting the matrix. Further, the hollow member may be made of a material different from the material constituting the matrix. In this case, a melting point of the material constituting the hollow member is higher than a melting point of the material constituting the matrix.

The present invention has been described in line with the above embodiments, but the present invention is not limited to the configurations of the above embodiments, and includes various alterations, modifications, and combinations that would be made by a person skilled in the art within the scope of the invention according to Claims. 

1: An up-drawing continuous casting method for forming a casting having a predetermined shape by drawing up molten metal held in a holding furnace, the up-drawing continuous casting method comprising: introducing a hollow member into the molten metal, the hollow member configured to draw up the molten metal; and flowing inert gas into the hollow member so as to pour the inert gas into the molten metal. 2: The up-drawing continuous casting method according to claim 1, further comprising: forming the casting by drawing up the molten metal with the hollow member after stopping the flowing of the inert gas into the molten metal. 3: The up-drawing continuous casting method according to claim 1, further comprising: introducing a plurality of hollow members into the molten metal; and flowing the inert gas into at least one of the plurality of hollow members so as to pour the inert gas into the molten metal. 4: The up-drawing continuous casting method according to claim 1, wherein: a mold release agent is provided in at least part of the hollow member. 5: The up-drawing continuous casting method according to claim 4, further comprising: separating the part of the hollow member from the casting formed by the molten metal solidifying, the part of the hollow member being provided with the mold release agent. 6: The up-drawing continuous casting method according to claim 1, further comprising: spraying coolant gas on the molten metal drawn up with the hollow member, when the hollow member is drawn up. 7: The up-drawing continuous casting method according to claim 1, wherein: the hollow member is immersed in the molten metal, the molten metal is drawn up with the hollow member at the time of drawing up the hollow member immersed, the molten metal being drawn up with the hollow member due to a surface film of the molten metal, a surface tension of the molten metal, and wettability between the molten metal and the hollow member, and, the molten metal drawn up is cooled off to form the casting. 8: An up-drawing continuous casting apparatus for forming a casting having a predetermined shape by drawing up molten metal, the up-drawing continuous casting apparatus comprising: a holding furnace configured to hold the molten metal; a hollow member configured to draw up the molten metal; a driving portion configured to draw up the hollow member so as to draw up the molten metal with the hollow member; and a gas supply portion configured to supply inert gas into the hollow member. 9: The up-drawing continuous casting apparatus according to claim 8, wherein: the driving portion draws up the molten metal with the hollow member after stopping flowing of the inert gas into the molten metal. 10: The up-drawing continuous casting apparatus according to claim 8, wherein: a plurality of hollow members is provided; and the gas supply portion flows the inert gas into at least one of the plurality of hollow members so as to pour the inert gas into the molten metal. 11: The up-drawing continuous casting apparatus according to claim 8, wherein: a mold release agent is provided in at least part of the hollow member. 12: The up-drawing continuous casting apparatus according to claim 8, further comprising: a cooling portion configured to spray coolant gas on the molten metal drawn up with the hollow member, when the hollow member is drawn up. 13: The up-drawing continuous casting apparatus according to claim 8, wherein: the molten metal is drawn up with the hollow member at the time of drawing up the hollow member immersed, the molten metal being drawn up with the hollow member due to a surface film of the molten metal, a surface tension of the molten metal, and wettability between the molten metal and the hollow member, and the molten metal drawn up is cooled off to form the casting. 14: A continuous casting comprising: a matrix having a unidirectional solidified structure extended in a longitudinal direction; and a dualphase extended in the longitudinal direction, wherein: the dualphase is constituted by a hollow member. 15: The continuous casting according to claim 14, wherein: a plurality of hollow members is provided. 16: The continuous casting according to claim 14, wherein: the hollow member is immersed into molten metal, the molten metal is drawn up with the hollow member at the time of drawing up the hollow member immersed, the molten metal being drawn up with the hollow member due to a surface film of the molten metal, a surface tension of the molten metal, and wettability between the molten metal and the hollow member, and the molten metal drawn up is cooled off to form the continuous casting. 